1. Field
The disclosed subject matter relates to a self-raising headrest for a vehicle seat. More particularly, the disclosed subject matter relates to a headrest that self-raises in a fold-flat vehicle seat, whereby the headrest that is stowed against the seat upon folding of the seat returns to its extended position upon opening of the seat from the folded position to the unfolded position.
2. Brief Description of the Related Art
Passenger vehicles typically include a multitude of safety features to protect the occupants from harm during impact collisions. For example, seatbelts, airbags and active restraint systems have been employed in vehicles for many years. The safety features are designed to minimize the destructive forceful impact on the vehicle occupants that may be caused, for example, when a vehicle suffers a head-on collision, as well as providing protection when the vehicle is struck from behind in a rear-end collision. The amount and quality of such safety systems may vary among vehicle manufacturers, and most modern manufacturers also incorporate headrest restraints to protect the vehicle occupants in rear-end collisions. An effective headrest is one that is typically located directly behind the centerline of the occupant's head and is positioned no more than about two inches away from the head.
In a front-end collision, the vehicle's forward motion is abruptly stopped. The seat belts and airbags prevent the occupants from hurtling forward. The goal is to maintain the occupant in an upright position and to prevent his/her body from striking into hard surfaces, other occupants, or from being ejected out of the vehicle.
Conversely, in a rear-end collision, the impact forces are directed in the opposite direction. The vehicle is abruptly propelled forward, and the seated occupants are correspondingly thrown backward. Just as the seatbelt and/or airbag holds an occupant in the seat and restricts forward motion, a seatback and head restraint restricts rearward motion in a rear-end collision.
Importantly, the headrest should be positioned so that the occupant's head does not pivot over the headrest in a rearward direction. This pivoting action over the headrest could flex the upper spinal column. For example, an adjustable head restraint placed in a relatively lower position by a shorter person may not fit a subsequent, taller person whose head and upper spinal column can flex over the head restraint in a rear impact collision.
In U.S. Pat. No. 2,989,341, there is described a stationary reclining chair having a headrest that is extended to a pre-determined supporting position during the initial reclining movement of the chair. The reclining chair employs a combined guiding and actuating linkage in the form of a double arm actuating lever so that the pivotal mount moves in a prescribed arcuate path about the backrest pivot in response to the user's reclining movement. As the user sits in the upright chair and leans against the backrest, the corresponding force on the linkage engages the linkages and guiding mechanisms of the headrest to the extended position in order to support the back of the user's head. Further application of rearward force against the backrest of the chair causes the extended headrest and backrest to move as a single unit with no relative displacement between the backrest and headrest from the initial inclined position. Thus, the increase in angular relationship between the backrest and the chair seat does not change the relative position of the headrest in relation to the backrest in the further-reclined chair.
Also, PCT publication WO94/01302 provides a vehicle seat having a foldable backrest and a head restraint (i.e., headrest), where the headrest can be retracted into the backrest when folded down, and returned when the backrest is folded up. As the backrest is progressively folded down, a blocking device which normally maintains the backrest in an upright locked position is released, and a link arm pulls a yoke rod downwardly into the backrest, thereby retracting the headrest against the backrest. However, the device contains a significant limitation in that folding the vehicle seat upward returns the headrest to the “lowermost position of the adjustment range”, which must then be manually moved upward by hand to a higher adjustment position.
Further, U.S. Patent Publication No. US2002/0079723A1 discloses a mechanical actuating apparatus for a headrest mounted on a seat back which is able to be folded downward. The headrest is reportedly completely retracted from its pre-adjusted position and then restored to the original position when the seat back is folded upward. The traction device used is a Bowden cable, wherein the traction wire is connected to the headrest holder and allegedly counteracts the pulling force of an energy storing device which pulls the headrest into an extended position. The pivoting movement of the seatback is converted into a rolling-up or unrolling movement to extend or shorten a free length of the cable of the traction device. Unfortunately, the device is particularly limited by the use of such a Bowden cable traction mechanism, since the cable may slide out of position or become jammed.
Therefore, typical vehicle headrest restraints, including those described above, are deficient in their ability to provide a simple mechanism for a self-retracting headrest that minimizes clearance requirements for folding seatbacks. Moreover, a headrest restraint that returns to an extended position immediately upon unfolding of the backrest would be advantageous in providing greater safety for a user who can adequately adjust the headrest to match the user's head location as he/she sits in the vehicle seat, while simultaneously eliminating the situation where the user's head could pivot over the fully-retracted headrest during a vehicle collision.